Cause of arrivals delays at LAX still up in air

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Editor's note: This story was updated at 2:30 p.m. Aug. 14, 2006, to clarify when the delays occurred.

A disturbance to the signal of a landing navigation system at Los Angeles International Airport caused 46 arrival delays the morning of Aug. 7, Federal Aviation Administration officials said.

The navigation equipment, called the Instrument Landing System (ILS), helps pilots land planes when visibility is limited. Conditions that day near the airport were hazy.

ILS, which is ground-based, broadcasts precise directional signals. These signals provide the pilot with a lateral and vertical path to the runway.

At 8:46 a.m. PST, ILS shut itself down, a safety feature that kicks in when there is a problem with the signal. It is unclear what caused the signal interruption, officials said. The area around ILS was under construction, but FAA officials could not confirm whether the signal failure was related to that construction.

FAA officials ruled out the possibility that equipment error or the system’s age were responsible for the signal obstruction.

"The system is not old.... The age of the system had nothing to do with the problem,” FAA spokeswoman Laura Brown said. Technicians “couldn’t find anything mechanically or electronically wrong with the system. We may not be able to determine what created the problem with the signal that caused the ILS to shut itself down.”

By 11:50 a.m. PST Aug. 7, the skies had cleared enough so that the ILS wasn’t necessary. It was returned to service at 12:18 p.m. PST. By 3 p.m., there were no delays.

The same system experienced signal issues early Aug. 6. ILS shut itself down, was manually reset and came back online. It also had a signal problem the night of Aug. 5, but was able to reset itself without shutting down. FAA officials said neither glitch caused any delays.

To prevent potential recurrences, the airport is keeping all trucks and construction equipment away from the ILS components, FAA officials said yesterday.

Since implementing the new procedures at the airport, no further disruptions have been reported.